1. Field of the Inventions
The present inventions relate generally to shaft-based instruments and, more particularly, to shafts for use in golf clubs and other shaft-based instruments.
2. Description of the Related Art
Over the years, there have been a variety of attempts to improve shaft-based instruments such as golf clubs, ski poles and hockey sticks. With respect to golf clubs, many substitutes have been introduced for the hard wood shafts originally used in golf club drivers and irons. Early substitute materials included stainless steel and aluminum. More recently, carbon fiber reinforced resin shafts have become popular. Such shafts are typically hollow and consist of a shaft wall formed around a tapered mandrel. The use of fiber reinforced resin has allowed golf club manufacturers to produce shafts having varying degrees of strength, flexibility and torsional stiffness. Carbon fiber reinforced resin shafts have also become popular in other shaft-based instruments. As such, manufacturers are able to produce shafts which suit the needs of a wide variety of applications.
Nevertheless, manufactures of shaft-based instruments are faced with a variety of design issues that have proven difficult to overcome using conventional fiber reinforced resin technologies. One issue associated with shaft design is related to the torsional and longitudinal stiffness of the shafts and, in the golf club shaft context, the attempts of designers to increase torsional stiffness (especially near the club head) in order to improve shot accuracy and increase longitudinal stiffness in order to cope with the ever increasing swing velocities of golfers. Another issue associated with shaft design is the location of the shaft flex point. More specifically, the inability of shaft designers to precisely predict the location of the flex point when designing a shaft without using excessive amounts of composite material, which can lead to weight and thickness issues, can be problematic. Breakage prevention is another important design issue. With respect to golf club shafts, for example, breakage often occurs within the region of the main body section that is adjacent to the club head.